CVE-2020-28211 in EcoStruxure Control Expert
Summary
by MITRE • 11/20/2020
A CWE-863: Incorrect Authorization vulnerability exists in PLC Simulator on EcoStruxureª Control Expert (now Unity Pro) (all versions) that could cause bypass of authentication when overwriting memory using a debugger.
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Analysis
by VulDB Data Team • 12/09/2020
The vulnerability identified as CVE-2020-28211 represents a critical authorization flaw classified under CWE-863, which specifically addresses incorrect authorization conditions in software systems. This weakness affects the PLC Simulator component within EcoStruxureª Control Expert, which has since been rebranded as Unity Pro, impacting all versions of the software. The vulnerability manifests through a dangerous condition where authenticated users can potentially bypass authorization mechanisms when performing memory overwrite operations through debugger interfaces. This flaw fundamentally undermines the security model of the industrial control system environment where such simulators are commonly deployed.
The technical implementation of this vulnerability stems from insufficient validation of user privileges during memory modification operations within the debugger functionality of the PLC Simulator. When users attempt to overwrite memory locations using debugging tools, the system fails to properly verify whether the current user context has appropriate authorization levels to perform such operations. This incorrect authorization check creates a pathway for privilege escalation where unauthorized or unprivileged users might be able to execute memory modification actions that should be restricted to administrators or authorized personnel only. The vulnerability specifically exploits the gap between the authentication mechanism and the authorization enforcement during active debugging sessions.
The operational impact of this vulnerability extends beyond simple unauthorized access to potentially compromising entire industrial control systems. In industrial environments where PLC simulators are used for development, testing, and validation of control logic, this flaw could enable attackers to inject malicious code or manipulate system behavior during the simulation phase. The implications are particularly severe because the PLC Simulator serves as a testing ground for control systems that will eventually be deployed in production environments, meaning that any modifications made during simulation could directly affect operational technology infrastructure. This vulnerability aligns with ATT&CK technique T1059.006 for Command and Scripting Interpreter and T1068 for Exploitation for Privilege Escalation, as it enables unauthorized users to perform actions that should require elevated privileges.
Security professionals must recognize that this vulnerability represents a significant risk to industrial cybersecurity posture, particularly in environments where operational technology and information technology systems converge. The flaw exposes the underlying assumption that memory modification operations within debugging contexts are properly controlled, which is often not the case in legacy industrial software implementations. Organizations utilizing EcoStruxure Control Expert or Unity Pro software should prioritize immediate assessment of their debugging environments and implementation of compensating controls such as network segmentation, restricted access controls, and mandatory privilege reviews. The vulnerability underscores the importance of proper authorization enforcement in industrial control systems and highlights the need for comprehensive security testing of development environments that interface with production systems. This weakness also demonstrates how seemingly benign debugging functionality can become a critical security risk when authorization controls are improperly implemented, making it essential for security teams to conduct thorough vulnerability assessments of industrial control system development tools.